Fruit trees typically do not carry all of the fruit that initially sets. For example, the "June drop" is a way that the tree naturally sheds excess fruit. With a young tree, the crop should be thinned dramatically early in the season because the tree is not mature enough to be able to bear a full crop successfully. If you did not thin the fruit, then the tree will drop some of it as a means of self-thinning until it comes into balance.